This invention relates generally to methods and apparatus for storing energy and, more particularly, to energy storage systems for high-altitude, light weight, long duration solar powered aircraft, and related methods.
Aircraft are used in a wide variety of applications, including travel, transportation, fire fighting, surveillance and combat. Various aircraft have been designed to fill the wide array of functional roles defined by these applications. Included among these aircraft are balloons, dirigibles, traditional fixed wing aircraft, flying wings and helicopters.
One functional role that a few aircraft have been designed to fill is that of a tightly stationed (i.e., maintained in a small, laterally and vertically limited airspace), high-altitude (e.g., stratospheric), long-duration platform. Operating from high, suborbital altitudes at temperatures well below the freezing point of water, such aircraft can operate as communication relay stations between ground-based and space-based stations. However, to have truly long flight durations, the aircraft must either carry enough fuel to last extreme lengths of time or have the ability to refuel and/or recharge its energy storage system.
Given the broad range of functions that a long-duration, tightly stationed, suborbital platform has the potential to perform, it is desirable to design such platforms to be capable of handling larger payloads and power demands, which typically drain resources necessary to maintain flight through a full range of typical weather conditions.
One potential source of power that can be used to recharge an aircraft's energy storage is solar power. However, solar power is intermittent, and solar-powered aircraft must have significant energy storage systems to store enough energy to fly through each night during a flight.
Therefore, there exists a definite need for apparatus and related methods for repeatedly storing and discharging energy. Preferably, using such methods, such an apparatus should be able to operate up to very high, suborbital altitudes for a long period of time. Importantly, it is desirable for such apparatus to have significant energy storage capacity while weighing as little as possible. Furthermore, it is preferable for such an apparatus to be relatively inexpensive to build, maintain and operate and, furthermore, be relatively pollution-free. Various embodiments of the present invention can meet some or all of these needs, and provide further, related advantages.